Semiconductor translating device



W.- SHOCKLEY SEMICONDUCTOR TRANSLATING DEVICE March 16, 1954 2 Sheets-Sheet 1 Filed May 28, 1949 INVENTOR W. SHOC/(LEV ATTORNEY Mareh 1954 w. SHOCKLEY 2,672,528

SEMICONDUCTOR TRANSLATING DEVICE Filed May 28, 1949 2 Sheets-Sheet 2 FIG. 5

FIG. 6

IN l/ENTOR By M. SHOC/(LEV ATTORNEY Patented Mar. 16, 1954 SEMICONDUCTOR TRANSLATING DEVICE William Shockley, Madison, N. 3., assignor to Bell Telephone Laboratories, Incorporated, New York, N. Y., a. corporation of New York Application May 28, 1949, Serial No. 96,059

11 Claims.

This invention relates to semiconductor signal translating devices and more particularly to such devices of the general type disclosed in the applications, Serial No. 35,423, filed June 26, 1948 and Serial No. 89,969, filed April 2'7, 1949 of W. Shockley.

Translating devices of the type disclosed in the applications above identified, which are of the class of devices which has come to be known as transistors, comprise a body of semiconductive material. a pair of spaced connections to the body, and a third large area or ohmic connection to the body at a region spaced from the first-mentioned connections. The two spaced connections are designated as the emitter and collector and the large area or ohmic connection is termed the base. Amplified replicas of input signals impressed between the emitter and base are obtained in a load circuit connected between the collector and base.

A structural feature of such devices is that the collector connection, or both the emitter and collector connections, is defined by a zone in the semiconductive body of conductivity type opposite that of the body. For example, the body may be of N conductivity type germanium and the transformation of a surface region of the body to P conductivity type.

In the operation of such devices, a substantial 'direct current bias obtains between P and N regions at the collector. The transition region or junction between the collector and body is of small thickness, for example of the order of centimeter in an illustrative device, so that at a surface area of the body intersected by this region a very strong field exists. Consequently, current leakage may occur across this region or junction at the surface of the body. Such leakage is a source of random, spurious variations or noise in the output of the device.

One object of this invention is to reduce such variations, thereby to increase the signal to noise ratio for the translating device and, hence, to

enhance its performance.

In accordance with one general and broad feature of this invention, leakage currents at the intersection of a P-N junction or transition region and the surface of the semiconductive body are inhibited by controlling the fields in the .vicinityof this intersection.

Such control may be effected in one way, in accordance with a specific feature of this invention, by tapering the zone defining the collector toward the intersection, thereby to reduce the gradient across the transition region at the surface.

The control may be effected also, in accordance With another specific feature of this invention, through the agency of an auxiliary or guard electrode upon the collector zone and in proximity to the intersection region aforenoted, this electrode being operated at ground potential for alternating current signals. The bias of this electrode may be the same as that of the collector; however, for some structures it may be biased at a small voltage relative to the base, for example of the order of that on the emitter.

The invention and the above-noted and other features thereof will be understood more clearly and fully from the following detailed description with reference to the accompanying drawing in which:

Fig. 1 shows diagrammatically a semiconductor signal translating device illustrative of one embodiment of this invention;

Fig. 2 illustrates one way in which the tapered collector zone in the device of Fig. 1 may be formed;

Fig. 3 illustrates another manner in which a tapered zone of one conductivity type may be produced upon a body of the opposite conductivity type; I

Fig. 4 illustrates still another way in which such a tapered zone may be produced.

Fig. 5 is a perspective view of a semiconductor signal translating device illustrative of another embodiment of this invention;

Fig. 6 is a sectional view of the device of Fig. 5, showing the configuration of the converted zones in one face of the semiconductor body; and

Fig. 7 is a plan view of a translating device illustrative of another embodiment of this invention.

Illustrative of the semiconductor materials which may be utilized in devices constructed in accordance with this invention is N conductivity type germanium produced as disclosed in l3 and [4, for example platings of rhodium, are made to the zones or regions ii and I2 respectively and serve as the emitter and collector connections respectively. A third ohmic connection I5, which also may be for example a coating of rhodium, is applied to the peripheral part of the N-type body In and serves as the base connection.

In a typical device, the body lo may be a disk of the order of 0.20 centimeter in diameter and 0.01 centimeter thick and the emitterand collector zones H and I2 respectively may be circular and of the order of 0,002 centimeter thick.

These zones II and [2 may be producedby nuclear bombardment of the opposite faces of the N-type body It] in the manners disclosed in the application, Serial No. 89,969, referred to hereinabove. a

In the operation of the device, the base is grounded, asshown, and the output circuit includingthe load I6 and a biasing 'source i'lis connected between the. base and [the collector connection I I4. The collector is biased in the reverse direction relative to the body ill, that is, at a negative potential which may be of the order 016 10 to 100 volts, by the source I1. 7 The input "circuit compri'singthe alternating current signal source 'Ii8, a resistor f9 and a biasing source ifiis connected between the ba'seand the emitter connection 13, as shown.. The bias applied by "the source maybe or 'the order of 1 volt and usually is positive although some applications it may, be ne ative. ,Am'plified replicas of sig- .nals applied between the emitter i3 and base [5 by. the source f8 appearac ss the load l6.

' I .Ih'e transition region '24 between the P-type eollector zone 12 and the body 16 intersects the surface in which the P-type zone i 2 appears. Be-

jcau'se of the potentialfdifference between the collector l2 and the 'body il'll leakage currents, may flow across the intersection of this transition region with the surface noted. Such leak 'lag e currents giyeris e to random variations or noise in the output or load circuit, In order to reduce the fields and, hence, the leakage curre'n ts across :the intersection, the JP -type zone l2 is tapered near its margin, as illustrated in 1.

.. Such tapermay be realized in one. wayas illustrated in Fig. 2 by controlling the direction jandintensity of radiation ofthe nuclearparticies emanating from the source S and directedagainst ,the body III, to produce the marginalportion of the Zone 2-. si ila i r a behproduc inanother way illustrated in Fig. 3 by forming a ."sfurf'ace layer JIZ'Aof uniform thickness upon the N-type body [0A 'and then grinding away the peripheral portion of the layer and the body. In order to further reduce such currents in theoutput circuit, an auxiliary, or guard electrode 2|, which maybe annular and coaxial with the coll ector connection l4 and in the form or a rhodium plating, is provided upon the P-type zone I2 in the vicinity of the intersection above noted. Thisguard electrodeji, is connected to th'ebase by way of a condenser 22 and, therefore,

order to reduce the resistive load on the collector, the thickness of the P-type region between the collector and the guard electrode is mad small and this material is made of only Weak P-type. The guard electrode 2| serves in the nature of a suppressor to prevent noise due to leakage across theintersection of the transition region 24 with the. surface.

The tapered form of P-type region together with a small area intersection between the transition regionand the surfac or" the body Iil may be produced also in the manner illustrated in Fig. As shown in this figure, nuclear particles emanating from the source S are controlled in intensity. and direction by a filter 25 and projected against the body [BB through a slit or aperture in a mask 26 adjacent the surface of the body I0 andimpenetrable to the nuclear particles. The source S may be a a naturally radio active one producing alpha particles, for example pol onium, plutonium or radium. Becaus of the direction of the alpha particles a conical wedge-shaped zone of P-type material i213 is formed inthe litypebody IOB. Asimilar formof zon'e 12B cand be produced when the conversion of N to P-type is effected by nuclear particles projected b'ya suitable accelerator, by varying the orientationfof the body HUB with respect to the direction of incidence of the nuclear beam thereon.

In the embodiment of this 'inventien illus- .trated in Figs. 5 and 6, the N-type wafer I Q'D,

for example of high backivolta'ge N conductivity type germanium, has in one iacethereo f a layer of P conductivity type, tl'i'isv layer comprising a central, circular relatively thick portioniil, an annular relatively thick portion '31 concentric with the central portion "38 and a thin annular e 3 xt n bet th ce tr l V ndernular portions 30 and 3|. The layer comprises l an u er ma i .33...??tFQd fr the a n a p r 3L. T e. e e alror iq of the layer ma rep d e n ev iins th N- ype b dy ateria o -ivp ma erial. b nu le r, bo ba dm nt, th va ous t ickne se be g. Pro ed. b m l na indiv d ll .9 jointly the nature, energy or direction of the bomba n p l sqr x m l t s. la e may be produced by first converting a thin surface :l re e wa e v"mic P-typ b boma e t a p rarti c an than. bomar h re ns. r ond to he Phrqn .35 an film-W1 de r n l er at ve y.

the several regions or portions may be produced by bombarding the surface with'nuclearparticles ofpne ki and c ntr n th ne y o d r ction of th particles to effect deeper conversion of N to P-type material at the regions 30 and 3|. In an illustrative device, the diameter of the collector E63 and the width of theemitter {'39 and auxiliary or guard electrode 210 may be 0.095 centimeter, the guard electrode, maybe spaced 0.025 centimeter, edge to edge, 'iromthe collector 'and the emitter and collectormay be spaced 0.014 centimeter, the width ofthe zone 32 being 6.01 centimeter. The zones 32 and,

may be 0.0004 centimetervthick and the zones 39 and El may be 9.002 centimeter thick. 'The pecentimeter from the intersection of thejunction 245 with the surfaceof theblockor body I60.

Ohmic collector and emitter connections m and I38 respectively, which may be rhodium 'platings, are 'rnade'to'the "thicker isms 3'0 and 3'l 'A similar ohmic baseconnection "[Eill isinadeto the opposite surface ofthe bod'ylil'ii. Anannuler auxiliary or guard electrode connection 2II'I is provided to the marginal portion 33 inside of and in the vicinity of the intersection-between the transition region 240 and the surface of the body I00 having the P-type layer therein.

In the operation of the device, the collector I40 is biased negative, for example of the order of to volts, with respect to the base I50. The emitter connection I is biased at a small potential, for example of the order of 1 volt negative, with respect to the base I and the auxiliary or guard electrode also is biased slightly negative, also of the order of 1 volt, with respect'to the base. As a result of signals impressed upon the emitter, the resistance of the thin web 32 is modulated whereby variations in th collector current corresponding to the signals impressed upon the emitter are produced. Advantageously, in order that highly effective modulation may be realized, the web 32 should be very thin, for example of the order of 4 10 centimeters and form with the N-type body I00 an abrupt junction with a high capacity across the transition layer or region.

The auxiliary or guard electrode, as in the device disclosed in Fig. 1 and described heretofore, serves to suppress noise due to leakage currents flowing across the intersection between the transition region 240 and the surface of the body or wafer I00.

The device illustrated in Fig. 7 is a modification of that illustrated in Figs. 5 and 6 and described hereinabove. The collector connection MBA is provided with a pluralit of parallel and oppositely extending projections or teeth which are in interleaved relation with similar teeth on the emitter connection I 30A. The auxiliary or guard electrode 2IOA encompasses the emitter connection and is disposed between it and the intersection of the transition region; 240A with the surface of the semiconductive N-type body IO0A. It will be understood that, as in the device shown in Figs. 5 and 6, the P-type regions below the teeth and body of the emitter and collector connections are relatively thick and the P-type webs between each tooth of the collector and the adjacent teeth of the emitter are relatively thin similar to the web 32 in Fig. 6.

Although specific embodiments of this invention have been shown and described, it will be understood that they are but illustrative and various modifications may be made therein without departing from the scope and spirit of this invention.

What is claimed is:

1. A signal translating device comprising a body of semiconductive material of one conductivity type, having on one face thereof a zone of semiconductive material of the opposite conductivity type, base, emitter and collector connections to said body, said collector connection contacting said zone, and auxiliary electrode means encompassing said collector connection and contacting said zone adjacent the periphery thereof.

2. A signal translating device comprising a body of N-type semiconductive material having on one face thereof a zone of P-type material, a collector connection to said zone, emitter and base connections, one of which is to the opposite face of said body, a guard electrode upon said zone and encompassing said collector connection and adjacent the intersection of the junction between said zone and body and said one face, a first circuit connected between said emitter and base connections, a second circuit including 6. means biasing said collector connection in the reverse direction relative to said body, and means biasing said guard electrode in said reverse -direction and at a lower potential than the bias on said collection connection.

3. A signal translating device in accordance with claim 2 wherein the marginal portion of said zone decreases in thickness toward said intersection.

4. A signal translating device comprising a body of semiconductive material of one conductivity type having in one face thereof a zone of the opposite conductivity type, a collector connection to said zone, an emitter connection to the opposite face of said body, a base connection to said body, and an auxiliary electrode upon said zone adjacent the margin thereof.

5. A signal translating device comprising a body of germanium of one conductivity type and having in one face thereof a zone of the opposite conductivity type, an ohmic connection to said zone, a rectifying connection to said body opposite said zone, a base connection to said body, and a guard electrode upon said zone adjacent the margin thereof.

6. A signal translating device comprising a body of N-type germanium having in one face thereof a zone of P conductivity type, a collector connection to said zone, an emitter connection to said body opposite said zone, a base connection to said body, means biasing said collector connection negative with respect to said base connection, an auxiliary electrode upon said zone adjacent the periphery thereof and encompassing said collector connection, means biasing said auxiliary electrode negative with respect to said base and at a potential lower than the bias upon said collector connection, and a direct alternating current connection between said auxiliary electrode and said base connection.

7. A signal translating device comprising a body of N-type germanium having in opposite faces thereof zones of P conductivity type, one of said zones having its marginal portion tapering toward the respective face of said body, an output circuit including a collector connection to said one zone, an input circuit including an emitter connection to the other of said zones, at base connection to said body, and a guard electrode upon said one zone, adjacent the periphery there of, encompassing said collector connection and grounded to said base connection for alterating current.

8. A signal translating device comprising a body of semiconductive material of one conductivity type having on one face thereof a layer of the opposite conductivity type, emitter and collector connections to spaced regions on said layer, a base connection to said body, and a guard electrode upon said layer, adjacent the periphery thereof and disposed about said emitter and collector connections.

9. A signal translating device comprising a body of semiconductive material of one conductivity type having in one face thereof a zone of the opposite conductivity type, a first ohmic connection to said zone, a second ohmic connection to said zone and encompassing said first connection. a third ohmic connection to said zone adiacent the periphery thereof and encompassing said second connection, and a fourth connection to said body remote from said zone.

10. A signal translating device comprising a body of semiconductive material of one conductivity type having on one face thereof a layer of the opposite-conductivity:typmusaid'ilayer having two. substantially concentric: relatively: thick: rergibns-aconnected by at reiativelysthiniweb,aapair offohm'i'c connections to saidzlayerropposite said two regions, a third: ohmic: connection-1 to-said layen' atvan area extending; about thetouiserr of said two;regions;.andafourthconnection-to said body;ataaxregion 'spacedz from said layer;

11. A signal translating device comprising; a body! of 1 N type': germanium having: on one; face thereof: a; layeruof P conductivity type; said layer including-.5 a central relatively thiclezone;- an .1 an nular: relatively thick zone encompassing: and

substantially concentric with said centralazone 5 opposite face: ofsaid body.

WILLIAM? SI-IO-CKIJEYC References Gited in the file of. this? patent UNITED STATESPATENTS Number; Name Date 23476323 Rack July 19,1949 2,486,776 Barney Nov. 1,,1949' 2;524;035I Bardeen et a1. Oct. 3,,1950' 

